<?php
// 这里是比较两个字符串的相似度
class LCS {
  var $str1;
  var $str2;
  var $c = array();
/*返回串一和串二的最长公共子序列
*/
function getLCS($str1, $str2, $len1 = 0, $len2 = 0) {
  $this->str1 = $str1;
  $this->str2 = $str2;
  if ($len1 == 0) $len1 = strlen($str1);
  if ($len2 == 0) $len2 = strlen($str2);
  $this->initC($len1, $len2);
  return $this->printLCS($this->c, $len1 - 1, $len2 - 1);
}
/*返回两个串的相似度
*/
function getSimilar($str1, $str2) {
  $len1 = strlen($str1);
  $len2 = strlen($str2);
  $len = strlen($this->getLCS($str1, $str2, $len1, $len2));
  return $len * 2 / ($len1 + $len2);
}
function initC($len1, $len2) {
  for ($i = 0; $i < $len1; $i++) $this->c[$i][0] = 0;
  for ($j = 0; $j < $len2; $j++) $this->c[0][$j] = 0;
  for ($i = 1; $i < $len1; $i++) {
    for ($j = 1; $j < $len2; $j++) {
      if ($this->str1[$i] == $this->str2[$j]) {
        $this->c[$i][$j] = $this->c[$i - 1][$j - 1] + 1;
      } else if ($this->c[$i - 1][$j] >= $this->c[$i][$j - 1]) {
        $this->c[$i][$j] = $this->c[$i - 1][$j];
      } else {
        $this->c[$i][$j] = $this->c[$i][$j - 1];
      }
    }
  }
}
function printLCS($c, $i, $j) {
  if ($i == 0 || $j == 0) {
    if ($this->str1[$i] == $this->str2[$j]) return $this->str2[$j];
    else return "";
  }
  if ($this->str1[$i] == $this->str2[$j]) {
    return $this->printLCS($this->c, $i - 1, $j - 1).$this->str2[$j];
  } else if ($this->c[$i - 1][$j] >= $this->c[$i][$j - 1]) {
    return $this->printLCS($this->c, $i - 1, $j);
  } else {
    return $this->printLCS($this->c, $i, $j - 1);
  }
}
}
 ?>
